In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production of semiconductor devices. Moreover, recently, as a next generation technique for a lithography process using ArF excimer lasers (193 nm), lithography processes using EUV (extreme ultraviolet radiation; wavelength of approximately 13.5 nm) and electron beams have been proposed and researched (for example, see Patent Documents 1 to 3). Exposure with electron beam or EUV is generally conducted in a vacuum.
Further, in EUV lithography, due to a high degree of linearity of EUV, the exposure apparatus is generally constructed by employing a reflective optical system which uses a mirror such as a multilayer film mirror.
On the other hand, one example of a resist material which satisfies high resolution conditions required for reproducing patterns of minute dimensions is a chemically amplified resist, which includes a base material component with a film-forming capability, and an acid generator component that generates acid on exposure. Chemically amplified resists include negative compositions, which undergo a reduction in alkali solubility on exposure, and positive compositions, which display increased alkali solubility on exposure.
Presently, as a base component of a chemically amplified resist, a resin is used. For example, in a positive resist, a polyhydroxystyrene resin is used in which some of the hydroxyl groups are protected with acid dissociable, dissolution inhibiting groups, or a (meth)acrylic resin is used in which some of the carboxyl groups are protected with acid dissociable, dissolution inhibiting groups (for example, see Patent Documents 4 and 5).
In a process using electron beam or EUV, improvement of sensitivity is required from the viewpoint of throughput and the like.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2003-177537
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2003-140361
Patent Document 3: Japanese Unexamined Patent Application, First Publication No. 2003-75998
Patent Document 4: Japanese Unexamined Patent Application, First Publication No. Hei 5-249682
Patent Document 5: Japanese Patent (Granted) Publication No. 2,881,969